1. Field of the Invention
This invention relates to a camera which is loaded with a film cartridge which contains a roll of film strip wound around a cartridge spool and a light lock door rotated closed to prevent ambient light from entering the cartridge interior through a film egress/ingress slot and rotated open to permit film movement into and out of the cartridge interior through the film egress/ingress slot.
2. Description of Related Art
In recent years, a new type of film cartridges have been proposed and have been put in the market. Such a film cartridge has a film egress/ingress slot and is provided with a light lock door rotatable between a closed position in which the cartridge interior where substantially the entire length of film strip wound around the cartridge spool is contained is kept light-tight and an open position in which the filmstrip is permitted to move into and out of the cartridge interior through the film egress/ingress slot. One of this type of film cartridges is known from, for example, U.S. Pat. No. 5,025,274. The film cartridge shell at one of its ends has at least two different symbol windows in the shapes of, for example, a circle (.smallcircle.) and a cross (X). The circular-shaped symbol window effects an indication that the filmstrip is unexposed, and the cross-shaped symbol window effects an indication that the filmstrip is exposed. An indicator rotatable together with the cartridge spool on the inside of the film cartridge is visible in different color from the cartridge shell in one specific angular position through the circular-shaped symbol window to provide an indication that the filmstrip is unexposed. The indicator is visible in different color in another specific angular position through the cross-shaped symbol window to provide an indication that the filmstrip is exposed.
Various types of cameras have been proposed for use with this type of film cartridges. This type of camera has a camera body provided with a cartridge chamber for receiving a film cartridge (which is hereafter referred to as a cartridge receiving chamber) therein. The cartridge receiving chamber at one of its ends has an opening through which is opened to permit a film cartridge to be loaded into and taken out of the cartridge receiving chamber and which is closed by a lid locked in a locked position by a locking key. The camera is further provided with a rotational spool driver which is brought into engagement with the cartridge spool when the film cartridge is inserted into the cartridge receiving chamber and rotates the cartridge spool in opposite directions to forcibly move the filmstrip into and out of the cartridge interior through a film egress/ingress slot, and a light lock door driver which is brought into engagement with the cartridge spool when the film cartridge is inserted into the cartridge receiving chamber and rotates the light lock door in opposite directions to open and close the film egress/ingress slot.
Low-priced cameras of this type has a film rewind switch which is turned on to rotate a motor-driven spool driver for causing rotation of the cartridge spool to rewind an exposed filmstrip into the film cartridge and turned off when an exposure counter indicates zero. The cartridge spool of such a camera is not always located in a fixed position when the rewind switch is turned off, and consequently, the indicator of the film cartridge is not always precisely in a fixed angular position relative to the symbol window which effects an indication that the filmstrip has been exposed. Accordingly, there is a necessity for the photographer to make an additional rotation of the indicator to adjust the indicator in position relative to the symbol window prior to taking the film cartridge out of the camera. Specifically, in this type of low-priced camera, the motor-driven spool driver has a spool drive shaft with a key engageable with a key way of the cartridge spool. Because the angular position of the key way is precisely specified with respect to the spool driver shaft, the spool driver has to be rotated for precise angular position adjustment of the indicator relative to the symbol window prior to taking the film cartridge out of the camera. Another necessity encountered by the photographer is to operate the light lock door driver to rotate the light lock door open to permit film movement into and out of the film cartridge prior to loading the film cartridge into the camera and to rotate it closed prior to taking the film cartridge from the camera for prevention of ambient light from entering the cartridge after permit film movement into and out of the film cartridge after taking the film cartridge out of the camera.
It is hard in the economical point of view to built a motor drive mechanism for both angular position adjustment of the indicator and operation of the light lock door in the low-priced camera.